Generator Transfer Switch

[Scotty]

We have a newish 2016 Winnebago Navion with the QC 3600 watt Onan-Cummings LP generator.

I can't tell from the owner's manual whether the generator needs to be plugged in to work and then unplugged when on shorepower or is this all automatic?

Is there a transfer switch that automatically (or manually) uncouples from shore power if I start the generator?

How do I know if the 110 volt outlets in the RV are being fed from shorepower or from the generator? It can't be both.... Or maybe some are generator-fed and some are shorepower fed?
thanks,
Scotty

[Winterbagoal]

If you have an AutoTransferSwitch, it's function would be described in the owner's manual.
My 2018 Navion doesn't have one. I have to manually plug the 30A shore power cord either into the generator 30A output outlet in the rear driver's side storage compartment, or into a shore power source.
Look inside the compartment where your shore power cord is stored for a 30A outlet fed from the generator. It looks like an electrical junction box, which it is.
In my rig, all the AC outlets inside the coach are fed from the shore power cord, whether it's actually plugged into shore, or the generator outlet. If I'm off grid, my inverter powers some of the AC outlets by converting 12VDC power from the coach batteries into 110AC.

[BobC]

In some ways, although somewhat less convenient, the plug-in method can be preferable to an automatic transfer switch (ATS). ATSs can fail or malfunction due to loose wire connections, arcing, relay failures, etc. There are many threads on Winnieowners and other forums that attest to this.

Personally, even though I have an ATS, I've never had the need for it. I'm either camping with shore power or without, so the need for an automatic changeover has never been a must-have. Without the ATS, I would have plugged the generator into the correct outlet as part of my set-up. I suppose that, if it was storming outside and my shore power failed it would be nice to not have to go out in the rain to switch over but that's never happened to me (but I do live in California).

[Morich]

It looks like you have what might be called "manual transfer switch" rather than automatic but that is certainly not a bad thing in my view as it makes it much less likely to fail! The difference is that you have a choice of where to plug the cord. Into shore power and not need the generator or when you are moving from one site to the next, when you unplug from the shore power, wind up the cord and plug it into the box that feeds power from the generator. Pretty simple and slick as it does then let you just stop on the roadside, start the genset and you have AC power to all the places you did when plugged in!
Simple and very reliable as long as you don't forget to unplug!!!

[Scotty]

Ok, I get it now. It is the ultimate manual transfer switch, with the owner making the transfer of the plug manually from either shore power or generator power.

That does make some sense. I can see that it is about as bulletproof as a switch can be, and also allows the use of all the same 110volt outlets. Only the input has been changed.
I can live with that.

Only downside is that it would nice if the plug was a locking type instead of just a push plug. Although come to think of it, a twist-locking plug might not work with that diameter electrical cable. What the heck is that shore cable anyway? And why? It handles one tenth the amps of my welding cable, along with less voltage.... and seems vastly oversized and rigid. Does anyone ever replace the shore cable with something more manageable in cold weather?
Thanks, Scotty

[Scotty]

Originally Posted by Morich

It looks like you have what might be called "manual transfer switch" rather than automatic but that is certainly not a bad thing in my view as it makes it much less likely to fail! The difference is that you have a choice of where to plug the cord. Into shore power and not need the generator or when you are moving from one site to the next, when you unplug from the shore power, wind up the cord and plug it into the box that feeds power from the generator. Pretty simple and slick as it does then let you just stop on the roadside, start the genset and you have AC power to all the places you did when plugged in!
Simple and very reliable as long as you don't forget to unplug!!!

Morich, thanks for that reply and especially for the picture. I see now that there is no electrical wiring between the generator socket box and the and the box next to it which contains the shore line and the control panel connections.
Just knowing that makes me it much easier to understand the way it is wired as a manual transfer.

I am considering changing the shore line to a longer lighter gauge version of itself. Something easier to handle than that monstrous short, thick shore connection it came with as OEM. I can't see any reason for that heavy shoreline, but interested in what you think.

[Winterbagoal]

Originally Posted by Scotty

Morich, thanks for that reply and especially for the picture. I see now that there is no electrical wiring between the generator socket box and the and the box next to it which contains the shore line and the control panel connections.
Just knowing that makes me it much easier to understand the way it is wired as a manual transfer.

I am considering changing the shore line to a longer lighter gauge version of itself. Something easier to handle than that monstrous short, thick shore connection it came with as OEM. I can't see any reason for that heavy shoreline, but interested in what you think.

Voltage drop?

[BobC]

I'd leave the size of the cord alone. MH cords are indeed hefty. They're large since they're designed to carry many more amps than your typical home extension cord. The insulation is heavier as well in order to stand up to the elements and wear. Your's is a 30A cord which is designed to carry twice the amperage of a typical 15A home extension cord.

You also mentioned a locking plug. You can easily replace the plug on the MH end of your with a twist-loc 30A plug but you'll also have to change out the receptacles. An easier solution might be to secure the cord in some way so it doesn't easily pull loose (Velcro?).

[Scotty]

Originally Posted by Winterbagoal

Voltage drop?

Well, you put your finger on exactly what it is that bothers me. I've spent the morning doing voltage drop and wire heating calcs, on that original shore line - this monster cable which looks to be sized to minimize voltage drop. It's made as if it was expected to be carrying a battery DC current with low voltage and high amps. To do that it needs to be made short with heavy gauge conductors like any battery cable.

But that's not what the shore line does, so why is it built like it is? A 30 amp shore line is either carrying 120 VAC from the hookup post to the RV, or 120 VAC from the generator to the RV. Those are max amps, but not all that high heatwise. And we know that voltage drop isn't nearly as significant when we start with 10x the voltage.

There's a lot of electrical things about this RV that seem odd to me. This is just one more.

[JerryP]

My 2017 View has the same manual plug configuration.

I have heard that some people turn the 120V receptacle 180 degrees in it's housing in order to make the easier to plug in the male plug. Haven't tried this yet.

I would not change the power cord to a smaller wire gauge. I would be concerned about safety issues. Also, it gets easier to stuff the cord into the small space the more times you do it.

Regards,
Jerry

[bkg]

Originally Posted by Scotty

Well, you put your finger on exactly what it is that bothers me. I've spent the morning doing voltage drop and wire heating calcs, on that original shore line - this monster cable which looks to be sized to minimize voltage drop. It's made as if it was expected to be carrying a battery DC current with low voltage and high amps. To do that it needs to be made short with heavy gauge conductors like any battery cable.

But that's not what the shore line does, so why is it built like it is? A 30 amp shore line is either carrying 120 VAC from the hookup post to the RV, or 120 VAC from the generator to the RV. Those are max amps, but not all that high heatwise. And we know that voltage drop isn't nearly as significant when we start with 10x the voltage.

There's a lot of electrical things about this RV that seem odd to me. This is just one more.

I just made a post on my ATS install here should that be of interest to you.

On your shore cord concern - I recommend NOT TO downgrade your shore cord. It is beefy for two reasons; insulation (insulated thick jacket for the "rough service" and protect it from the elements) and the conductor size, appropriate for the amp draw for 30 amps. Because the shore cord is made of stranded cable, stranded cables exhibit 20 to 50% more attenuation than solid copper conductors. And because the cross section of a stranded conductor is not all copper (there’s some air in there), therefore requiring more strands to equal the load design of solid wire.
Typically, the weakest point for shore cord is the plug/receptacle. The surface contact points are seldom tight. So, inside that plug, a lot of the current is trying to make it through the small amount of surface that has reasonable contact. When the contact point decreases or load increases the heat increases which is why you typically see plug melt-down.

Bobby

[NeilV]

Originally Posted by bkg

I just made a post on my ATS install here should that be of interest to you.

On your shore cord concern - I recommend NOT TO downgrade your shore cord. It is beefy for two reasons; insulation (insulated thick jacket for the "rough service" and protect it from the elements) and the conductor size, appropriate for the amp draw for 30 amps. Because the shore cord is made of stranded cable, stranded cables exhibit 20 to 50% more attenuation than solid copper conductors. And because the cross section of a stranded conductor is not all copper (there’s some air in there), therefore requiring more strands to equal the load design of solid wire.
Typically, the weakest point for shore cord is the plug/receptacle. The surface contact points are seldom tight. So, inside that plug, a lot of the current is trying to make it through the small amount of surface that has reasonable contact. When the contact point decreases or load increases the heat increases which is why you typically see plug melt-down.

Bobby

Yes indeed!

They are typically 10/3 for a 25 foot cord but may be 6/3 for a 100 foot run on the 30 amp cords which is really not excessive. A contractors 20 Amp job site 120 Volt AC cord will be a 12/3 or 10/3. Remember that unlike extensions cords which are mostly for intermittent heavy loads a shore power cord is made to carry constant heavy loads under extreme heat and cold conditions along with use in wet locations.

I stay at many camps where its over 50 feet to the power pole so 6/3 is the best choice as the minimum wire size for a 30 amp power cord which still may get a tad hot if there are long term brownouts which if you staying in a camp ground is highly likely situation to encounter.

Many find that voltage at campgrounds can drop well below damaging levels so its pretty common to install power protection devices with automatic low voltage cut outs or buck and boost transformers to raise voltage back to equipment safe levels. Personally I went with an Autoformer which is a Automatic Boost Transformer and it has dramatically reduced the failure rate of electrical components in my Motor Home. Nothing ruins a camping trip in the Deep South where effective temperatures are hovering at 115+ degrees like a burnt out Air Conditioning Compressor, Blower Fan Motor or the very common start capacitor/hard start device failure.

Anyways you do not want the last connection inside your electrical bay to be the weakest link in the system especially during a low voltage event so I would not downsize that short cord that jumpers between shore and generator power even if it was a 4/3. You really do not want to meet the minimum spec possible on your shore power wiring.

[Scotty]

I just checked the original equipment - which is the heavy 20 foot long cord with the 30 amp male connection end. This is the cord supplied by Winnebego for our 2016 Navion. The use is as a manual transfer switch depending on the owner to select to jumper between shore power and generator power.

I mentioned I might replace it with a much lighter cord that was not so bulky and hard to handle.

I still might. The original is large heavy black plastic OD - mostly of a poly-plastic insulation. But to my surprise the wires in there are simply ten gauge. I had expected them to be a larger size. But under that mass of insulation they are simply 10 gauge stranded.....and not a particularly high strand count....which doesn't help either. There are better materials available to make a more usable cord that is easier to handle with specs that match the specs on this OEM cord .

However, upgrading the cord is expensive. Better cord starts by costing 3x as much per foot. And goes up from there.

It looks to me that the OEM is the cheap $$ solution and easy to improve.
There are 3-conductor ten gauge flexible cables available that are much easier to handle in the cold and just as good spec-wise for wear and voltage. Look at marine, industrial, or aviation power sources.

I must say that after doing some maintenance and upgrades this fall that I am not impressed with the wiring and electrical material decisions in the 2016 Navion. No, they aren't bad, but certainly are not "best quality". If Navion was to offer an upgrade option in various system quality I would buy it, and like to think I'm not alone.

Scotty - ex-K5EZK, an old engineer, machinist ... and yes, I'm a bit picky on quality.